c$++11\mathrm{.}9($Package Inheritance Hierarchy$)$ Package$-$delivery services, such as

FedEx ${?}^{},$ DHL ${?}^{}$ and UPS ${?}^{},$ offer a number of different shipping options, each

with specific costs associated. Create an inheritance hierarchy to represent

various types of packages. Use class Package as the base class of the hierarchy,

then include classes TwoDayPackage and OvernightPackage that derive from

Package $.$

Base$-$class Package should include data members representing the name, ad$-$

dress, city, state and ZIP code for both the sender and the recipient of the pack$-$

age, in addition to data members that store the weight $($in ounces$)$ and cost per

ounce to ship the package. Package $\text{'}$s constructor should initialize these data

members. Ensure that the weight and cost per ounce contain positive values.

Package should provide a public member function calculatecost that re$-$

turns a double indicating the cost associated with shipping the package.

Package $\text{'}$s calculatecost function should determine the cost by multiplying

the weight by the cost per ounce.

Derived$-$class TwoDayPackage should inherit the functionality of base$-$class

Package $,$ but also include a data member that represents a flat fee that the

shipping company charges for two$-$day$-$delivery service. TwoDayPackage $\text{'}$s con$-$

structor should receive a value to initialize this data member. TwoDayPackage

should redefine member function

so that it computes the ship$-$

ping cost by adding the flat fee to the weight$-$based cost calculated by base$-$

class Package's calculatecost function.

Class OvernightPackage should inherit directly from class Package and con$-$

tain an additional data member representing an additional fee per ounce

charged for overnight$-$delivery service. OvernightPackage should redefine

member function calculatecost so that it adds the additional fee per ounce

to the standard cost per ounce before calculating the shipping cost. Write a test

program that creates objects of each type of Package and tests member func$-$

tion calculatecost.